1. Field of the Invention
The present invention relates to paging receivers, and more particularly, to a method for controlling the power supplied to an RF (Radio Frequency) receiver in a paging receiver.
2. Description of the Related Art
A paging receiver uses a battery as a power source. Thus, in order to minimize power dissipation, the paging receiver supplies power to an RF receiver in the paging receiver on a periodic (non-continuous) basis.
In a conventional paging system, paging data is asynchronously transmitted in POCSAG code. Section A of FIG. 1 is a waveform diagram of the paging data, which consists of preamble data PD and batch data BD. The preamble data PD is a reversal code which switches between "1" and "0" during 576 bits, and enables the paging receiver to detect the asynchronously transmitted paging data. The batch data BD consists of a plurality of batches, each having a sync code for synchronizing a codeword and a plurality of frame data. As shown, the paging system transmits the paging data in irregularly alternating intervals (asynchronously).
In order to minimize power dissipation and facilitate failure free reception of paging data from the paging system, the paging receiver blocks (cuts off) power to the RF receiver for a specific time interval (.DELTA.T) which is less than the transmission time interval for the preamble data PD. Then, the paging receiver supplies (unblocks) power to the RF receiver for a predetermined time interval during which the RF receiver can receive the transmitted data and check whether the received data is preamble data PD. That is, the paging receiver repeatedly blocks and supplies power to the RF receiver for the time AT and the predetermined time, respectively.
Section B OF FIG. 1 is a waveform diagram illustrating the state (i.e., blocked or unblocked) of the power supplied to the RF receiver in the paging receiver. The high state of the waveform of FIG. 1B corresponds to the paging receiver supplying power (unblocked) to the RF receiver, and the low state corresponds to the paging receiver blocking power to the RF receiver. The paging receiver decodes the data received from the RF receiver and then, judges whether or not the received data is preamble data PD. If the decoded data is preamble data PD, the paging receiver drives (sets) the RF receiver in (to) a batch mode in order to enable the RF receiver to receive the batch data following the preamble data PD. However, if the decoded data is not preamble data PD, the paging receiver continues to check whether or not preamble data PD is being received, while repeatedly supplying and blocking power to the RF receiver.
It is to be appreciated that since the paging system transmits paging data asynchronously, the paging receiver cannot predict when paging data is going to be transmitted in order to timely supply power to the RF receiver. Therefore, in order to facilitate failure free reception of the paging data transmitted from the paging system, the conventional paging receiver periodically supplies power to the RF receiver for a specific time interval (.DELTA.T) which is shorter than the transmission time interval for the preamble data PD, including during an idle interval where the paging system does not transmit paging data. Accordingly, even when the paging system does not transmits paging data, the paging receiver supplies power to the RF receiver unnecessarily, thereby wasting power.